Atmospheric pressure ionization (API) mass spectrometry is a novel form of mass spectrometry in which ionization is carried out in a small reaction chamber external to the low pressure region of a quadrupole mass spectrometer. An analytical system based on a combination of a high pressure-high speed liquid chromatograph, an API mass spectrometer and a computer has been designed and will be evaluated for use in biologic studies. The aim of this work is to introduce mass spectrometric methods into clinical chemistry, and to provide new chemical methods for studying human disorders. New gas chromatographic methods are also under study. A GC-MS-COM analytical system with high resolution glass open tubular capillary columns will be assembled and used in the analysis of biologic mixtures.